On-vehicle non-aqueous electrolyte secondary batteries used as, for example, driving power supplies for electric vehicles (EV) and hybrid electric vehicles (HEV, PHEV) are provided with pressure detection type current shut-off mechanisms in addition to safety valves for explosion protection. The pressure detection type current shut-off mechanisms is disposed in such a way as to be actuated by a gas rapidly generated in the inside of a battery under abnormal conditions and prevent burst or ignition of the battery by shutting-off a current inflow.
As for the non-aqueous electrolyte secondary battery, an increase in charging voltage has been known as one of techniques to increase the battery capacity. Also, it is known that an overcharge inhibitor, e.g., tert-amylbenzene, biphenyl (refer to PTL 1), cycloalkylbenzene compounds, or compounds having quaternary carbon adjacent to a benzene ring (refer to PTL 2), is added to a non-aqueous electrolytic solution as a safety measure when a non-aqueous electrolyte secondary battery is brought into an overcharge state. However, if the charging voltage is increased to improve the battery capacity, the overcharge inhibitor is decomposed even at a voltage set as a usual working range depending on the type of the overcharge inhibitor, so that degradation of battery characteristics and degradation of safety after charge-discharge cycle are feared.
It is also known that in order to solve such issues, the overcharge resistance is improved by adding lithium carbonate (Li2CO3) to a positive electrode mix of the non-aqueous electrolyte secondary battery (PTL 3). In the case where lithium carbonate is added to the positive electrode mix of the non-aqueous electrolyte secondary battery, when a high voltage is applied to the battery, for example, at the time of overcharge, carbon dioxide gas is generated from a positive electrode plate and, thereby, the pressure detection type current shut-off mechanism can be actuated reliably prior to the safety valve for explosion protection.